For a great number of years lithographing presses have been in use for printing on paper or paperboard. In this process, the water and ink are applied to predetermined surfaces of the printing plate, and the ink is then normally transferred to a blanket cylinder which acts to apply the ink to the web or sheet being printed. The plate cylinder is provided with a surface of zinc or similar material which is applied to the plate cylinder, and which may be removed when the surface to be printed is changed. The water is applied to the plate, and covers the area thereof which is not to be printed. The plate cylinder is also in contact with an ink roller which applies ink to the surfaces of the plate cylinder which are to be printed. The ink is normally transferred to a blanket cylinder which applies the ink to the sheet or web.
In general, this process is very old, and has been used for many years. However, there is one difficulty which is often experienced with this type of printing, particularly at high speeds, and that lies in the means of distributing the water in a thin film uniformly throughout the length of the cylinder.
If the cylinder bearing the film of water does not have a uniform coating throughout its length, a portion of the plate on the plate cylinder is not properly moistened, with the result that the ink is applied to a portion of the plate where it is not desired. As a result, the resulted printing material is blemished.
This invention relates to an improvement in cylinder moistening apparatus which is designed to distribute water evenly in a thin coating throughout the length of the cylinder or roller. As a result, the water is applied to the plate cylinder uniformly throughout the length of the cylinder, and many of the difficulties previously experienced with presses of this type are eliminated.